Thanks for the response. I got the issue solved by changing all prices in my shop to VAT included and added the full price to the ticket plus as well. Now it is constant.
The only trouble now is the divider: the never ending story as in Excel. I saw threads in 2015 so I don’t want to bother you but I guess it is still an open issue that you take over the currency settings of WOOCommerce.
In Germany obviously we use comma as decimal mark while in US it is a dot. My shop mixes it now because Woocommerce uses comma correctly, while the ticket plus show a dot: https://copterview.eu/events/kategorie/messe/messe-drohnenfuehrerschein/
Any idea if you change this one time?